The present invention relates to the field of leadframes used in packaging integrated circuits.
One important aspect of packaged integrated circuits (ICs) is their so-called Moisture Sensitivity Level or MSL, which reflects the degree to which the ICs resist moisture-induced stresses that can cause failure. The MSL of a packaged IC depends in part on the quality of the seal at the interface between the plastic encapsulating mold compound and the metallic leads that extend from the package.
The electronics industry is moving towards the use of lead-free plating materials for plating IC leadframes. Combinations such as nickel-palladium-gold (NiPdAu) are replacing current tin-lead (SnPb) solders. A typical configuration has an Ni layer having a thickness between 0.5 and 1.4 microns, followed by a Pd layer having thickness between 0.02 to 0.10 microns and an Au layer of thickness between 0.003 and 0.010 microns. However, with the higher reflow temperature (260 C for NiPdAu vs. 235 C for SnPb), along with relatively poor mold compound adhesion to the Au component, it is expected that MSL performance for NiPdAu-plated leadframes will be reduced by at least one or two levels compared to standard Ag/Cu leadframes.
It would be desirable to improve the MSL performance of leadframes plated with lead-free plating materials, such as NiPdAu-plated leadframes.